diff --git a/schemas/json/block.json b/schemas/json/block.json
index 12567a94941c6d..5059829b82d0e1 100644
--- a/schemas/json/block.json
+++ b/schemas/json/block.json
@@ -480,7 +480,10 @@
 		},
 		"styledClasses": {
 			"description": "An array of class names that have individual stylesheets. If defined, overrides the 'style' property on the frontend, loading styles only when the class is present.",
-			"type": "array"
+			"type": "array",
+			"items": {
+				"type": "string"
+			}
 		}
 	},
 	"required": [ "name", "title" ],